Department of Chemistry
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Item Template effect of innocent and coordinating anions on the formation of interpenetrated 2D and 3D networks: methyl orange and iodine sorption studies(RSC, 2020) Sarkar, MadhushreeA 2D Cd(II) coordination polymer [Cd2(L1)4(H2O)4][ClO4]4·5(H2O), CP1, was synthesized with 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (L1) while the use of benzene-1,3-disulphonate (L2) along with L1 resulted in a novel 3D Cd(II) coordination polymer, [Cd(L1)2(L2)]·2(H2O)·(CH3OH), CP2. CP1 attained a threefold interpenetrated 2D staircase network where the channels are filled with H2O and ClO4− anions. CP2 has a 3D interpenetrated structure and has small pores. The chemical nature and size of the pores of CP1 and CP2 are effective in adsorbing organic dye molecules. Selective adsorption of upto 96% of methyl orange (MO) within 10 min was observed in CP1 and CP2. CP2 was also studied for the adsorption and desorption of iodine. CP1 and CP2 showed luminescence and their solid state PL has a strong emission peak at ∼484 nm. The structural analysis of L1 and [HL1][ClO4] showed the effect of ClO4− on the supramolecular assembly and geometry of the molecules of L1.Item Crystal Engineering of Metal−Organic Frameworks Containing Amide Functionalities: Studies on Network Recognition, Transformations, and Exchange Dynamics of Guests and Anions(ACS, 2007-06-07) Sarkar, MadhushreeThe reactions of bis(pyridinecarboxamido)alkanes with copper(II) in the presence of various anions and solvent systems afforded several polymeric crystalline complexes with or without guest inclusion. The crystal structure analyses of these complexes reveal that the coordination networks observed here include open one-dimensional (1D) chains containing cavities and open (4,4)-networks with three types of packing modes, namely, mixed, offset−offset, and trigonal, doubly interpenetrated (4,4)-networks both in parallel and in perpendicular (diagonal/diagonal) modes and a three-dimensional pseudo-diamondoid (658-topology) network. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via N−H···O hydrogen bonds. The exchange of counteranions from the polymeric crystalline complexes was found to trigger the network transformations. The 1D chain, which has rectangular cavities, was transformed into a pseudo-diamondoid network upon exchange of ClO4- with PF6- anions. The exchange of anions from two-dimensional (2D) open (4,4)-networks resulted in 2D-interpenetrated networks. It was found that the reverse exchange that is expected to result in open networks from interpenetrated networks is not allowed. The guest molecules included in these networks range from small molecules such as H2O, EtOH, and CHCl3 to big aromatic molecules such as nitrobenzene, toluene, anisole, p-xylene, benzonitrile, and naphthalene. The exchange of guest molecules in crystal-to-crystal fashion was also found to trigger the transformations in the mode of packing of 2D layers.Item Role of Anions in Assembling the Coordination Polymers of Bis–pyridyl–alkanediamides(Wiley, 2016-12-21) Sarkar, MadhushreeFormation of Coordination Polymers (CPs) of an amide based flexible ligand, bis(3-pyridyl)butanediamide, has been found to be directed by the anion of the starting metal salt: a 1D network with rectangular loops was obtained with CuSO4 while a 2D network having two-fold parallel interpenetration was obtained with Cu(ClO4)2. In the 1D network, a π•••π interaction between C=O groups of the amide is present whereas the 2D network shows self-complementary amide-to-amide hydrogen bond. The reaction of the ligand with Cu(C6H5COO)2 results in a 1D chain, where the benzoate units are also coordinated to the Cu(II) centres. The conformational adjustments of the butyl spacer of the ligand in the CPs according to the requirements of the counter anions is observed in the present study. The role of the counter anions (ClO4−, SO42− and C6H5COO−) towards the formation of the CPs was monitored through the competitive reactions, where the ligand was allowed to react with Cu(NO3)2 in the presence of other three counter anions altogether at a time. Further, an understanding on the network stability was gained by studying the counter anion exchange reactions.